This invention relates to variable capacity vane compressors which are adapted for use as refrigerant compressors of air conditioners for automative vehicles.
A variable capacity vane compressor is known e.g. by Japanese Provisional Patent Publication (Kokai) No. 62-129593, which is capable of controlling the capacity of the compressor by varying the suction quantity of a gas to be compressed. According to this known vane compressor, there is provided a pressure chamber formed in one of side blocks of a cylinder accommodating a rotor and communicating a zone under lower pressure with a zone under higher pressure, and an inlet port the opening angle of which is variable in response to a difference between pressure within a first pressure chamber of the pressure chamber and pressue within a second pressure chamber of same. The first pressure chamber is communicated with the zone under lower pressure, and the second pressure chamber is selectively communicatable with the zone under higher pressure via a high-pressure communication passage and with the zone under lower pressure via a lower-pressure communication passage by means of a control valve device. The control valve device extends across the high-pressure communication passage and the low-pressure communication passage, and is adapted to close the low-pressure communication passage and similtaneously open the high-pressure communication passage when pressure within the zone under lower pressure exceeds a predetermined value, to thereby bring the compressor into full capacity operation, and to open the low-pressure communication passage and simultaneously close the high-pressure communication pasasage when the pressure within the zone under lower pressure is below the predetermined value, to thereby bring the compressor into partial capacity operation.
The above control valve device comprises a bellows disposed within the zone under lower pressure and having an internal pressure lower than the pressure outside the bellows, i.e. the pressure within the zone under lower pressure, and a valve body having its one end connected to the bellows for axial movement thereof, wherein the control valve device selectively opens and closes the low-pressure communication passage and the high-pressure communication passage through expansion and contraction thereof in response to changes in the pressure outside the bellows, i.e. the pressure within the zone under lower pressure.
However, according to such conventional vane compressor, if the bellows is broken, e.g owing to a pinhole or the like formed through the peripheral wall thereof and hence the inside and outside of the bellows are brought into communication with each other, the internal pressure of the bellows increases to cause the bellows to expand abnormally. Consequently, the control valve device continues to open the low-pressure communication passage, so that the compressor continues partial capacity operation, thus failing to exhibit required compression ability.